Analysis of Radon Mass Exhalation in Soil Samples from Fault Regions of Kolasib District Mizoram

10

I

https://doi.org/10.22214/ijraset.2022.39788

January 2022

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com

Analysis of Radon Mass Exhalation in Soil Samples from Fault Regions of Kolasib District Mizoram, India Laldingngheta Ralte1, Ramesh Chandra Tiwari2, Rosangliana3, Bijay Kumar Sahoo4 1, 2

Department of Physics, Mizoram University, Tanhril, Aizawl Mizoram, India Department of Physics, Govt. Zirtiri Residential Science College, Aizawl - 796001, Mizoram, India.

4 Radiological Physics and Advisory Division, Bhabha Atomic Research Centre (BARC), Mumbai – 400094, India.

3

Abstract: In order to identify the distribution of radon mass exhalation soil samples from fault regions of Kolasib District were obtained. These were measured and analysed using scintillation based smart RnDuo device. The soil samples were collected from three different points in each selected fault. The exhalation rates from different locations ranges from 2.3 mBq/kg/hr – 54.19 mBq/kg/hr with an average of 20.42 mBq/kg/hr. Gamma survey measurement was also carried out which ranges between 89 nSv/hr – 157 nSv/hr with an average of 117.13 nSv/hr. The correlation graph between mass exhalation and gamma survey was plotted and a very weak correlation was obtained.

Keywords: Radon, mass exhalation, soil samples, RnDuo, fault I. INTRODUCTION The main source of radiation comes from cosmic rays, solar radiation and radioactive elements from the earth. The atmosphere prevents a majority of radiations from cosmic and solar radiations from reaching the earth but decay of radioisotopes like uranium, 238

thoron, radium and radon. Radon is gas formed on the fourteenth step of sequence of U radioactive decay series and is being continuously formed in the soil and released in air. This radon gas released in the air occupies 43% of radiation received by human beings and is usually the reason of lung cancer[1-2].

The movement of radon inside the soil is called emanation where radon is released into small air or water contained in pores between soil and rock particles and when it arrives at the soil surface it exhales into the atmosphere. The movement of radon is achieved by means of diffusion, advection and by means of gas transport[3]. The concentration of radon in soil is influenced by soil moisture content, barometric pressure variations, temperature and structure of soil. Radon becomes environmental hazards when it remains concentrated in enclosed places such as houses, caves and mines. Indoor radon and its influence on health has been studied by many researchers and the main contributor to these indoor concentration are radon from the soil and its exhalation[4-5].

Therefore radon and its exhalation from the soil are significant in obtaining data to be used in indoor concentration as well as for baseline data for further studies.

The purpose of this study is to obtain data for exhalation rates from soil samples collected from fault regions of Kolasib district, Mizoram, India. The fault regions are selected because faults are also responsible for movement of radon through rocks inside the earth[6]. This is the first investigation done regarding mass exhalation in soil samples on fault regions of Kolasib district. The results from this investigation will provide data for further studies in the future.

In this work, the radon exhalation from soil samples collected from various fault regions of Kolasib District, Mizoram are measured along with gamma survey of each region. The results are compared with the exhalation of radon in some parts of India.

II. MATERIALS AND METHODOLOGY The study area is located at north-east of India on Kolasib district in the state of Mizoram which lies in the seismic zone V of seismic zonation map of India. The geographical sites where the soil samples were collected from the fault lines are as shown in Fig 1. Kolasib district is located on the north of Aizawl, which is the capital of the state Mizoram. It is a tropical region with moderate climate and the temperature varies from 11ºC to 24 ºC during the winter season and 18 ºC to 29 ºC during summer. The sampling area extends from N 23° 53' 29.57'' to N 24° 28' 16.1’’ latitude and E 092° 39'33.97'' to E 092° 47'41.09'' longitude.

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

77

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com

Fig 1: Study area of Kolasib district with sampling areas Soil samples were collected from 36 different locations within the study area as shown in Fig 1. The soil samples were collected in such a way that for each fault line on the area, three samples were collected by means of gardening tools. The soil is burrowed a few centimeters deep depending on the structure of soil and the top most soil is avoided when sampling the soil. The samples are then brought back to the lab where they are analysed.

The Radon content in soil was obtained by means of scintillation cell method using Smart RnDuo. It is a technologically advanced portable radon /thoron monitor, designed for multiple applications in radon and thoron studies. By diffusion process, sample gas is collected into a scintillation cell and passes through a progeny filter and thoron discriminator eliminating the progenies. The thoron discriminator does not allow the short lived thoron to pass thorough. The radon measurements in RnDuo are based on detection of alpha emitted from radon and its decay products formed inside a scintillation cell volume and are continuously counted by the PMT and the associated counting electronics.

Fig 2: Smart RnDuo

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

78

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com When measuring radon, the volume and mass are taken before placing them on the exhalation chamber. The sample is then placed in the chamber and fitted with the detector connected by signal cable to the main device. The samples are then measured for a cycle of 60 minutes for a minimum of period of 8 hours. Build up data of radon with elapsed time can be retrieved and least square fitting can be carried out using the equation:

J M C (t )   m  V Where C (t ) is

222

  t  Co 

 (1)

Rn concentration ( Bq m 3 ) at time t , Co is the

222

Rn concentration ( Bq m 3 ) present in the chamber

t  0 , M is the total mass of the dry sample (Kg). V is the effective volume (volume of detector + porous volume of 3 sample + residual air volume of mass exhalation chamber) (m ) . The porous volume (VP ) can be estimated using the following volume at

Eqn. (2)

M  VP  Vs     (2)    g Where Vs is the sample volume in the mass exhalation chamber.  g is the specific gravity of the sample which can be taken as 2.77 gm/cc for clay type soil material. t is the measurement time (hr).

Upon least square fitting of the data to the above equations one may obtain the rate of radon exhalation per unit mass of the sample

J m from the fitted parameters with the information of the mass M of the sample.

Along with soil samples collected, gamma survey was done in each region where samples were collected. This is carried out with Survey Meter PM 1405 by detection block on the basis of Geiger-Muller counter by transformation of photon to electropulses. The detection and transfer of measured data to the main microprocessor controller are carried out by the embedded microprocessor controller. The instrument’s output information is obtained on the LCD of the device. The measurement range for γ radiations is between the ranges of 0.1  Sv / hr – 100 mSv / hr . The measurements of gamma readings were detected using the survey meter at a distance of 1m above the ground.

III. RESULTS The results of the mass exhalation from soil samples collected from different fault lines calculated using Eqn. (1) are shown in table 1. The exhalation rate varies as seen from the data with minimum value of 2.3 at K25 and maximum of 54.19 mBq / Kg / hr at K36. The mass exhalation rates ranges from 2.3 mBq / Kg / hr – 54.19 mBq / Kg / hr with an average of 20.42 mBq / Kg / hr .

This is comparable with fault regions of Aizawl District, in which the values of radon exhalation range between 11.2 mBq / Kg / hr - 72.2 mBq / Kg / hr with an average of 39.92 mBq / Kg / hr [7]. The variation may be due to rainfall and moisture content in the soil as soil moisture content plays a significant role in exhalation [8]. The results obtained from this are also comparable to work done in Northern Rajasthan (14.96 mBq / Kg / hr ), Kangra District, Himachal Pradesh (19.91

mBq / Kg / hr ) and Kathmandu Valley, Nepal (6.4 mBq / Kg / hr )[9-11]. We can see that there are variations in different places when compared with each other. This may be due to differences in geology of the areas of study. The differences in structure of the land and soils play an important part in exhalation process. The presences of uranium in rocks underneath the earth are also the cause of high radon exhalation.

The gamma readings from soil samples collected from different fault lines are shown in table 1. The result ranges from 89 nSv / hr – 157 nSv / hr with an average of 117.13 nSv / hr . The maximum gamma reading is at K27 with a reading of 157

nSv / hr and minimum at K8 and K16 with both having values of 89 nSv / hr is shown in Fig. 4 The correlation graph between mass exhalation and gamma survey is shown in Fig 5. A very weak correlation was obtained and we 2

can see that the correlation value R = 0.086 which shows that the negative correlation.

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

79

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com Table 1: Measurement of radon mass exhalation rate and gamma survey from fault regions of Kolasib district Location code

K1

K2

K3

K4

K5

K6

K7

K8

K9

K10

K11 K12

K13

K14

K15

K16

K17

K18

K19

K20

K21

GPS Coordinate

Elevation 23 m N 24° 20' 45.23'' E 092° 40'08.88'' Elevation 36 m N 24° 20' 51.39'' E 092° 40'17.69'' Elevation 44 m N 24° 20' 58.15'' E 092° 40'32.85'' Elevation 260 m N 24° 15' 27.80'' E 092° 40'36.50'' Elevation 351 m N 24° 15' 11.15'' E 092° 40'37.48'' Elevation 431 m N 24° 14' 49.92'' E 092° 40'56.08'' Elevation 385 m N 24° 14' 52.80'' E 092° 41'36.26'' Elevation 410 m N 24° 14' 59.27'' E 092° 41'34.60'' Elevation 403 m N 24° 14' 41.37'' E 092° 41'24.56'' Elevation 474 m N 23° 53' 29.57'' E 092° 40'23.97'' Elevation 468 m N 23° 53' 39.61'' E 092° 40'25.25'' Elevation 447 m N 23° 54' 14.22'' E 092° 40'26.09'' Elevation 186 m N 23° 55' 59.81'' E 092° 40'19.32'' Elevation 138 m N 23° 56' 04.76'' E 092° 39'46.88'' Elevation 152 m N 23° 56' 00.50'' E 092° 39'33.97'' Elevation 271 m N 23° 57' 59.14'' E 092° 40'54.97'' Elevation 313 m N 23° 57' 19.59'' E 092° 41'04.06'' Elevation 311 m N 23° 57' 11.55'' E 092° 41'06.12'' Elevation 48 m N 24° 20' 58.1'' E 092° 45' 32.0'' Elevation 38 m N 24° 20' 57.5'' E 092° 45' 23.5'' Elevation 37m N 24° 20' 59.0'' E 092° 45' 16.6'' Elevation 49 m

Gamma Survey meter readings (nSv/hr)

Radon mass exhalation rate (mBq/kg/hr)

Error Percentage (%)

106

8.2

15

101

11.9

107

24.6

141

35.5

127

25.4

119

35.9

127

45.0

89

12.8

119

10.0

98

11.0

135

7.6

110

5.6

132

27.7

108

28.4

102

6.7

89

28.8

109

35.7

118

32.7

129

9.9

130

11.5

105

6.5

142

45.3

15

15

15

11

16

15 13

15

15 15

16

13

15

15

10

16

16

15

15

15

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

80

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com K22

N 24° 28' 11.5'' E 092° 46' 54.9'' Elevation 53 m N 24° 28' 16.1'' E 092° 46' 53.4'' Elevation 58 m N 24° 28' 15.7'' E 092° 46' 56.6'' Elevation 350 m N 24° 14' 56.4'' E 092° 41' 12.3'' Elevation 360 m N 24° 14' 55.2'' E 092° 41' 12.6'' Elevation 365 m N 24° 14' 52.3'' E 092° 41' 11.8'' Elevation 679 m N 24° 14' 12.85'' E 092° 48' 26.37'' Elevation 695 m N 24° 13' 55.04'' E 092° 48'24.42'' Elevation 683 m N 24° 13' 44.86'' E 092° 48'17.95'' Elevation 582 m N 24° 12' 06.28'' E 092° 48'30.34'' Elevation 587 m N 24° 12' 08.93'' E 092° 48'34.25'' Elevation 665 m N 24° 12' 23.88'' E 092° 48'04.52'' Elevation 717 m N 24° 06' 18.61'' E 092° 48'40.71'' Elevation 668 m N 24° 05' 41.82'' E 092° 48'15.32'' Elevation 834 m N 24° 06' 09.95'' E 092° 47'41.09''

K23

K24

K25

K26

K27

K28

K29

K30

K31

K32

K33

K34

K35

K36

13

130

45.7

157

26.2

120

2.3

127

9.8

145

21.6

14

127

18.95

16

92

15.27

15

8.76

16

17.68

16

111

21.80

14

114

9.50

16

115

11.46

13

110

4.05

16

112

54.19

14

15

15

15

13

112

106

Mass Exhalation rate (mBq/kg/hr)

60 50 40 30 20 10 0 K1 K3 K5 K7 K9 K11 K13 K15 K17 K19 K21 K23 K25 K27 K29 K31 K33 K35 Location Codes Fig 3: Radon mass exhaltion from fault regions of Kolasib District.

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

81

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com 180 160 Gamma reading

140 120 100 80 60 40 20 0 K1 K3 K5 K7 K9 K11 K13 K15 K17 K19 K21 K23 K25 K27 K29 K31 K33 K35 Location codes Fig 4: Gamma survey from fault regions of Kolasib District y = 0.3409x + 110.18 R² = 0.086

180

Gamma Reading

160 140 120 100 80 60 40 20 0 0

10

20

30 40 50 Mass exhalation rate Fig 5: Correlation graph between mass exhalation rate and gamma survey.

60

IV. CONCLUSIONS The averages of mass exhalation from fault regions of Kolasib district were obtained and comparable to other regions. The average values were higher than other regions due to differences in geology of the areas of study and due to the proximity of the fault lines.

Gamma readings obtained shows slight variations on different regions and the correlation between mass exhalation and gamma survey shows negative correlation.

V. ACKNOWLEDGEMENT The authors are thankful to the Board of Research in Nuclear Sciences, Department of Atomic Energy sanction number 36(4)/14/67/2014-BRNS/36016, Government of India, for providing financial assistance through the Research Project.

REFERENCES [1] [2]

J.D. Appleton, J. C. H. Miles and D.K. Talbot. Dealing with radon emissions in respect of new development: evaluationof mapping and site investigation methods for targeting areas where new development may require radon protectivemeasures. Nottingham: British Geological Survey.(2010) X.Lu., Loretta Y. Li and X.L. Zhang. An Environmental RiskAssessment of Radon in Lantian Karst Cave of Shaanxi, China.Water Air and Soil Pollution, (2009);198, 307–316.

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

82

International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538 Volume 10 Issue I Jan 2022- Available at www.ijraset.com [3]

T.f. YANG, C.Y. CHAU, C-H. CHEN,L.L. CHYI and J.H. JIANG. Exhalation of radon and its carrier gases in SW Taiwan. Radiat. Meas.,(2003); v.36, pp.425-429 [4] V. Duggal,R. Mehra, and A. Rani.An Investigation of factors influencing indoor radon concentrations in dwellings of Northern Rajasthan, India. Journal of the Geological Society of India. (2015);86(2), 173–180.

[5] R. Sivakumar. A study on indoor radiation dose, radon, thoron and progenies concentrations in a hilly area. Environmental Earth Sciences.(2016);75(11), 1–13.

[6] V.M. Choubey, K.K. Sharma and R.C. Ramola. Geology of radon occurrence around Jari in Parvati valley, Himachal Pradesh, India. J. Environ.

Radioact.(1997);34(2):139-147.

[7] Laldingngheta, Vanramlawma, Hmingchungnunga, L. Z. Chhangte, R.C.Tiwari, Rosangliana, B.Zoliana, B.K. Sahoo and T.K. Agarwal. Measurement of radon exhalation from soil samples in various fault regions of Aizawl district, Mizoram, India. Perspective and Trends in the Development of Science Education and Research (2018);198.

[8] M. Faheema and Matiullah. Radon exhalation and its dependence on moisture content from samples of soil and building materials.Radiaiton Measurements(2008);43(8),1458-1462 [9] V. Duggal, R. Mehra and A. Rani .Study of Radium and Radon Exhalation Rate in Soil Samples from Areas of Northern Rajasthan. Journal of Geological Study of India.(2015);86(3),331-336 [10] D.K. Sharma, A.Kumar, M. Kumar and S. Singh. Study of uranium, radium and radon exhalation rate in soil samples from some areas of Kangra district, Himachal Pradesh, India using solid-state nuclear track detectors. Radiation Measurements.(2003);36(1-6),363-366 [11] P. Parajuli, D. Thapa and B. R. Shah. Study of Radon Exhalation Rate in Soil Samples of Kathmandu Valley Using Passive Detector LR115. Inter J ChemPhys Sci.(2015);4(4),30-9

©IJRASET: All Rights are Reserved | SJ Impact Factor 7.538 | ISRA Journal Impact Factor 7.894 |

83